The present invention is directed generally to apparatus for separating or fractionating whole blood into its various individual components, and more particularly to a disposable centrifugal blood separator for use in such apparatus.
Intervivos blood processing apparatus, wherein the blood is taken from a live donor, passed through the apparatus, and then returned to the donor, has come into wide use during recent years. During passage through the apparatus, the blood may be separated or fractionated into its component parts, i.e., plasma, red blood cells, and white blood cells or platelets, and some portion of these fractions may be returned to the donor while other portions may be selectively retained within suitable storage means.
Various types of apparatus have been proposed for the intervivos processing of blood. One type of apparatus which has come into wide use is described in U.S. Pat. Nos. 3,489,145 and 3,655,123. This apparatus utilizes a centrifugal separator element in the form of a rotatably driven bowl-shaped outer shell within which a cylindrically shaped center or filter piece is suspended to form a narrow sleeve-shaped separation chamber of very precise dimensions. Fluid connections are established with the chamber by means of a rotating seal, the chamber having an axially-aligned inlet port at one end for admitting whole blood, and a trio of collection ports at the other end for removing red blood cells, white blood cells, and plasma components separated during centrifugation. The structure and operation of a rotating seal for conveying whole blood to the chamber and fractionated blood components from the chamber is described in U.S. Pat. No. 3,519,201.
A major drawback of centrifugal processing units of this type has been their high cost of manufacture. This has resulted primarily because of the very narrow spacing which must be maintained between the inner wall of the outer shell and the outer wall of the central filler in order to achieve efficient separation of the blood components during the very limited transit time in which the blood is actually in the processing chamber. Typically, a spacing of 1.0 to 1.5 mms is necessary for typical transit times of approximately three minutes. This dimension must be maintained with a high degree of concentricity of mixing of the recovered fractions is to be avoided. As a result, the outer shell has heretofore been formed with thick side walls to prevent any variation of the separation channel width during operation of the apparatus.
The need for thick walls has made it heretofore impractical to mold the inner and outer shells, since the desired thicknesses could not be molded with the necessary precision. Instead, such shells have been extruded and then individually machined, making the cost of manufacture too high for the disposable single-use favored for avoiding contamination.
The present invention is directed to a new and improved construction for the centrifugal processing chamber which enables the unit to be economically fabricated from plastic by known molding techniques while maintaining a processing channel width of 1.5 mm of less with a high degree of concentricity.